[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Cholinesterase inhibitors](https://durgical.com/en/pharmacology/classes/cholinesterase-inhibitors/) › Pyridostigmine [Pharmacology](https://durgical.com/en/pharmacology/) · [Cholinesterase inhibitors](https://durgical.com/en/pharmacology/classes/cholinesterase-inhibitors/) # Pyridostigmine The standard oral medicine for the weakness of myasthenia gravis. It lasts longer than neostigmine and causes fewer gut side effects. Updated 2026-11-01 - Class: [Cholinesterase inhibitors](https://durgical.com/en/pharmacology/classes/cholinesterase-inhibitors/) - Enzyme: Acetylcholinesterase - ATC code: N07AA02 - WHO Model List of Essential Medicines ✂**Acetylcholinesterase**Pyridostigmine ⓘ No crystal structure of pyridostigmine bound to acetylcholinesterase exists. The figure shows edrophonium, a close chemical relative with the same charged trimethylammonium head, in the active site of Torpedo (electric ray) acetylcholinesterase, which shares the human enzyme's gorge and catalytic serine. **Target in 3D:** Acetylcholinesterase. PDB structure 1AX9 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1AX9) · Drag to rotate · pinch to zoom ## Mechanism of action In myasthenia gravis, antibodies reduce the number of working acetylcholine receptors at the muscle end plate. Pyridostigmine carbamylates acetylcholinesterase, so each nerve impulse leaves more acetylcholine in the synapse for longer and reaches the remaining receptors. It treats the symptom (weakness), not the autoimmune cause. It is a quaternary amine and does not enter the brain. - Carbamylates acetylcholinesterase at the neuromuscular junction - Acetylcholine lasts longer in the synapse - More of the remaining receptors are activated - Muscle strength and endurance improve ## Pharmacokinetics **Absorption** Poorly absorbed by mouth, so oral doses are much larger than injected ones; regular and extended-release tablets and a liquid exist **Distribution** Does not cross the blood-brain barrier **Elimination** Mainly unchanged in the urine; lower doses may be needed in kidney disease **Onset and duration** Acts longer than neostigmine ## Indications - Myasthenia gravis (symptomatic treatment) [Myasthenia gravis →](https://durgical.com/en/conditions/myasthenia-gravis/) - Pretreatment of military personnel against certain nerve agents - Reversal of non-depolarizing muscle relaxants (injection) ## Adverse effects ### Common - Nausea, vomiting, diarrhoea and abdominal cramps - More saliva and bronchial secretions - Sweating and small pupils - Muscle cramps and fasciculations ### Serious (rare, important) - Cholinergic crisis: weakness that can involve breathing muscles and cause death - Bronchospasm in people with asthma ## Contraindications - Mechanical obstruction of the bowel or urinary tract - Particular caution in bronchial asthma ## Key interactions **Atropine and other antimuscarinics** Relieve gut side effects but can hide the early signs of overdose and let a cholinergic crisis develop **Succinylcholine** Prolonged neuromuscular block (class effect) **Aminoglycoside antibiotics** Can add neuromuscular block; people with myasthenia gravis are particularly susceptible ## What is monitored - Muscle strength, swallowing, speech and eyelid drooping through the day - Breathing: vital capacity in a crisis - Kidney function ## Administration and safety - Taken at set times; the timing is matched to when strength is most needed - Extended-release tablets are not crushed - Tablets absorb moisture: kept dry in their original container ## Nursing care - Give doses on time; a late dose can bring back weakness - Check swallowing before giving food or other oral medicines - Teach the signs of both crises: worsening weakness, trouble breathing or swallowing, heavy sweating or salivation - Keep atropine available ## Pregnancy and breastfeeding Safety in pregnancy and breastfeeding has not been established; benefits and risks are weighed, since uncontrolled myasthenia is itself dangerous. ## Memory aid PYRIdostigmine = «PRolonged, Yes, Relief In myasthenia»: the long-acting oral one for myasthenia. ## Test yourself Think of the answer, then tap the question to see it. ## How does pyridostigmine improve weakness in myasthenia gravis? By inhibiting acetylcholinesterase, so acetylcholine lasts longer and activates more of the receptors that the antibodies have spared. ## Why can routine atropine with pyridostigmine be risky? It masks the muscarinic warning signs of overdose, so a cholinergic crisis can develop unnoticed. ## Which organ eliminates pyridostigmine, and what follows from that? The kidney, mostly unchanged; people with kidney disease may need lower doses. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/pyridostigmine/) ## Related drugs - [Neostigmine](https://durgical.com/en/pharmacology/neostigmine/) - [Edrophonium](https://durgical.com/en/pharmacology/edrophonium/) - [Atropine](https://durgical.com/en/pharmacology/atropine/) ## Related conditions - [Myasthenia gravis](https://durgical.com/en/conditions/myasthenia-gravis/) [← Back to the class: Cholinesterase inhibitors](https://durgical.com/en/pharmacology/classes/cholinesterase-inhibitors/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [DailyMed - PYRIDOSTIGMINE BROMIDE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=36284496-e56e-466c-9b56-6007bb5bb699) (DailyMed (U.S. National Library of Medicine), 2026); [Pyridostigmine: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682229.html) (MedlinePlus (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 12 (McGraw Hill, 2023); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 59 (McGraw Hill, 2023). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/pyridostigmine/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/pyridostigmine/